Oh my! did a writer in an experienced aviation publication actually claim that the CFM56 engine supplanted P&W engines on narrow bodies because it is a turbofan? That claim would be in ignorance of the facts called JT3D and JT8D, which equipped large numbers of DC-8s, DC-9s, MD-80s, 707s, 727s, and classic 737s.

Surely the CFM56 succeeded because it was a more efficient turbofan - a new design, higher bypass than the 200 series JT8Ds - and because Boeing was able to figure out how to stuff its large fan under the low wing of popular 737.

Those interested in engine history might look at the prop-fan, designed and flight tested to greatly improve fuel economy. It proved un-necessary in the short term. But is the general configuration of the prop-fan what Rolls-Royce means by "open rotor" in the same publication?

Note too that Rolls-Royce is asking whether or not it is appropriate to increase maintenance costs to achieve fuel greater efficiency in a time of high fuel prices.